clnhlzmn / eeprom-circular-buffer

An implementation of Microchip app note AVR101

An implementation of Microchip app note AVR101

See AVR101 for details.

This library implements a circular buffer for eeprom memory. The API exposes an interface to read and write a chunk of bytes. Every write is performed in a new location in the buffer to avoid wearing out the eeprom. For example, if I call ee_cb_init with buffer_size set to 32 then the first 32 calls to ee_cb_write will use new locations for the writes. After the 32nd call the write location will wrap to the beginning of the buffer again. To make this work the location of the last written data must also be saved to the eeprom on every write. To avoid wearing that location it also uses a circular buffer.

API

struct ee_cb

To use this library you must create an instance of struct ee_cb and initialize it with ee_cb_init

ee_cb_init

Use this function to initialize struct ee_cb.

• param base_address

  This is the eeprom address where you would like the buffer to be located. The buffer must be large enough to hold (data_size + 1) * buffer_size bytes.

• param data_size

  This is the size of the data you would like to read and write to the buffer. For example: if you wanted to store an uint32_t then data_size would be 4.

• param buffer_size

  This is the number of eeprom locations to use for storage. For example: if you your eeprom has an endurance of 100000 writes and you set buffer_size to 8, then you will be able to perform at least 800000 writes before you experience eeprom corruption.

• params reader and writer

  These are pointers to functions that implement the actual reading and writing of the eeprom. They should match the prototypes given by ee_cb_reader and ee_cb_writer.

ee_cb_read and ee_cb_write

After successful initialization (ee_cb_init returned 0) the functions ee_cb_read and ee_cb_write can be used to read and write data_size bytes.

Please note that the behavior of ee_cb_write and ee_cb_read is undefined if the eeprom is not initialized such that all locations have the same value. This is typically performed during programming. For example: an AVR microcontroller eeprom gets all bytes initialized to 0xFF after a chip erase.